﻿using System;
using System.IO;
using System.Text;
// https://www.cnblogs.com/guyun/p/4262587.html 
#if false  //用法实例
#region 打开按钮 
/// <summary> 
/// 打开按钮 
/// </summary> 
/// <param name=“sender“></param> 
/// <param name=“e“></param> 
private void txtMenuOpen_Click(object sender, EventArgs e)
{
    string fName;
    OpenFileDialog openFileDialog = new OpenFileDialog();
    openFileDialog.InitialDirectory = "";//注意这里写路径时要用c:而不是c: 
    openFileDialog.Filter = "文本文档|*.txt";
    openFileDialog.RestoreDirectory = true;
    openFileDialog.FilterIndex = 1;
    if (openFileDialog.ShowDialog() == DialogResult.OK)
    {
        fName = openFileDialog.FileName;  
        txtBox.Text = System.IO.File.ReadAllText(fName,FileEncoding.EncodingType.GetType(fName));
    }
}
#endregion
#endif
namespace JoinBoxCurrency
{
    /// <summary> 
    /// 获取文件的编码格式 
    /// </summary> 
    public class EncodingTool
    {
        /// <summary> 
        /// 给定文件的路径，读取文件的二进制数据，判断文件的编码类型 
        /// </summary> 
        /// <param name=“file_name“>文件路径</param> 
        /// <returns>文件的编码类型</returns> 
        public static Encoding GetType(string file_name)
        {
            Encoding encoding = null;
            if (!string.IsNullOrEmpty(file_name) && File.Exists(file_name))
            {
                FileStream fs = new FileStream(file_name, FileMode.Open, FileAccess.Read);
                encoding = GetType(fs);
                fs.Close();
            }
            return encoding;
        }
        /// <summary> 
        /// 通过给定的文件流，判断文件的编码类型 
        /// </summary> 
        /// <param name=“fs“>文件流</param> 
        /// <returns>文件的编码类型</returns> 
        public static Encoding GetType(FileStream fs)
        {
            byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };
            byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };
            byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //带BOM 
            Encoding reVal = Encoding.Default;
            BinaryReader r = new BinaryReader(fs, Encoding.Default);
            int i;
            int.TryParse(fs.Length.ToString(), out i);
            byte[] ss = r.ReadBytes(i);
            if (IsUTF8Bytes(ss) || (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF))
            {
                reVal = Encoding.UTF8;
            }
            else if (ss[0] == 0xFE && ss[1] == 0xFF && ss[2] == 0x00)
            {
                reVal = Encoding.BigEndianUnicode;
            }
            else if (ss[0] == 0xFF && ss[1] == 0xFE && ss[2] == 0x41)
            {
                reVal = Encoding.Unicode;
            }
            r.Close();
            return reVal;
        }
        /// <summary> 
        /// 判断是否是不带 BOM 的 UTF8 格式 
        /// </summary> 
        /// <param name=“data“></param> 
        /// <returns></returns> 
        private static bool IsUTF8Bytes(byte[] data)
        {
            int charByteCounter = 1; //计算当前正分析的字符应还有的字节数 
            byte curByte; //当前分析的字节. 
            for (int i = 0; i < data.Length; i++)
            {
                curByte = data[i];
                if (charByteCounter == 1)
                {
                    if (curByte >= 0x80)
                    {
                        //判断当前 
                        while (((curByte <<= 1) & 0x80) != 0)
                        {
                            charByteCounter++;
                        }
                        //标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X 
                        if (charByteCounter == 1 || charByteCounter > 6)
                        {
                            return false;
                        }
                    }
                }
                else
                {
                    //若是UTF-8 此时第一位必须为1 
                    if ((curByte & 0xC0) != 0x80)
                    {
                        return false;
                    }
                    charByteCounter--;
                }
            }
            if (charByteCounter > 1)
            {
                throw new ArgumentException("非预期的byte格式");
            }
            return true;
        }
    }
}

